WO2002030567A1

WO2002030567A1 - Cordierite honeycomb structural body and method of manufacturing the structural body

Info

Publication number: WO2002030567A1
Application number: PCT/JP2001/008491
Authority: WO
Inventors: Kazuhiko Kumazawa; Kunikazu Hamaguchi
Original assignee: Ngk Insulators, Ltd.
Priority date: 2000-10-12
Filing date: 2001-09-28
Publication date: 2002-04-18
Also published as: ZA200204424B; DE60134341D1; JP2002121085A; EP1354629B1; JP4473438B2; US6726977B2; EP1354629A1; AU2001292281A1; US20030026944A1; EP1354629A4

Abstract

A honeycomb structural body, wherein a reinforcement part having cordierite powder carried thereon is formed at the end face of at least one opening of a base material of cordierite honeycomb structure, whereby an wear resistance at the end face of the opening can be increased without losing such a merit of a thin wall type honeycomb structural body that a pressure loss is small.

Description

TECHNICAL FIELD The present invention relates to a cordierite honeycomb structure and a method for manufacturing the same.

The present invention relates to a cordierite honeycomb structure suitably used as a catalyst carrier for purifying automobile exhaust gas, and a method for producing the same. Background art

In general, a catalyst for purifying automobile exhaust gas is used in a form supported on a carrier. As such a catalyst carrier, an 82-arm structure made of cordierite has been used. In particular, in recent years, exhaust gas regulations have tended to be tightened, and in response to this, the purifying performance of the catalyst has to be improved.Thus, the thickness of the partition walls is extremely thin compared to conventional thin-walled honeycomb structures. A body has been proposed.

A thin-walled honeycomb structure with a wall thickness of 100 m or less and an opening ratio of the end face of which may be 83% or more: (1) Since the heat capacity is low and the warm-up efficiency is high, The catalyst can be activated. (2) It has various characteristics that are favorable as a catalyst carrier, such as a high opening ratio, so that pressure loss when exhaust gas passes through the catalyst carrier can be reduced. ing.

However, the thin-walled honeycomb structure has a problem in that the opening end face exposed to high-pressure exhaust gas discharged from the engine is significantly worn due to the above structural characteristics. Particularly, in recent years, the catalyst (that is, the catalyst carrier) has been placed close to the engine for the purpose of improving the processing capacity, which is a factor that accelerates the wear of the opening end face.

As a means for solving such a problem, for example, a method of increasing the thickness of only the partition wall near the opening end face of the 82 cam structure (Japanese Patent Laid-Open No. 2000-51710) is described below. Applying glass components such as glaze and water glass In addition, a method of applying and firing a specific component of the cordierite-forming raw material (the same publication) has been studied.

However, in the method of increasing the wall thickness near the opening end face, the wear resistance of the opening end face is improved, but the end face opening ratio of the honeycomb structure is reduced, and the pressure loss is low. It is not preferable in reducing the merits. In addition, in the method of applying and firing glass components such as glaze, the applied part is densified and the strength is improved, but the part is made glassy and instead becomes brittle.The abrasion resistance is sufficiently improved I couldn't let it.

In addition, a method of applying and firing a specific component of a cordierite-forming raw material (a raw material that becomes cordierite by heat treatment such as firing, for example, a mixture of talc, alumina, kaolin, etc.) is performed by densifying the portion. Although it is possible to advance the temperature, it is not preferable in that the chemical composition of the coated portion deviates from the stoichiometric composition of the cordierite and the thermal expansion coefficient becomes high, thereby impairing the thermal shock resistance. Further, it is not sufficient in terms of abrasion resistance if only the area near the opening end face is densified by this method.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to reduce the advantages of a thin-walled honeycomb structure such as low pressure loss. Another object of the present invention is to provide a honeycomb structure excellent in abrasion resistance of an opening end face and a method for manufacturing the same. Disclosure of the invention

As a result of intensive studies by the present inventors, as a result of forming a reinforcing portion holding a cordierite powder on at least one opening end face of a honeycomb structure base material made of cordierite, The inventors have found that the problems can be solved and completed the present invention.

That is, according to the present invention, a honeycomb structure having a honeycomb structure made of a cordierite has a reinforcing portion carrying a cordierite powder on at least one opening end face thereof. Is provided It is.

As the cordierite honeycomb structure of the present invention, a cordierite honeycomb structure having a reinforcing portion in which cordierite powder is supported via a glass phase is preferable. The cordierite honeycomb structure of the present invention preferably has a reinforcing portion only at the opening end face of the base material and at a portion within 10 mm from the opening end face in the cell forming direction, and the partition wall of the base material has a thickness of 100 m. This effect is particularly exhibited when the following conditions are satisfied. .

Further, according to the present invention, a slurry containing a cordierite powder is adhered to at least one open end face of a fired or unfired honeycomb structure base material made of cordierite or a cordierite-forming material. After the drying, drying and Z or firing are provided.

In the production method of the present invention, it is preferable that the slurry containing the colloidal powder and the colloidal ceramic is applied, followed by drying and / or baking, and that the slurry containing the cordierite powder and the glaze is applied, followed by drying. Then, firing is preferable. BEST MODE FOR CARRYING OUT THE INVENTION

The cordierite honeycomb structure of the present invention has a reinforcing portion carrying a cordierite powder on at least one opening end surface of a base material having a honeycomb structure made of cordierite.

According to the present invention, there is provided an eighty-cam structure that does not reduce the advantages of a thin-walled honeycomb structure such as low pressure loss and has excellent abrasion resistance at the opening end face.

Hereinafter, the cordierite honeycomb structure of the present invention will be described in detail.

The cordierite 82 cam structure of the present invention (hereinafter, simply referred to as “82 cam structure”) is characterized in that it has a reinforcing portion carrying a cordierite powder. In such a reinforcement, the cordierite powder is In addition to filling the air holes in the wall of the cordierite honeycomb structure and welding through the firing process, the honeycomb structure is denser and has a lower porosity than other parts, so that the wear resistance of the parts is improved. In addition, since the reinforcing portion supports a cordierite powder of the same material as the base material, the difference in thermal expansion coefficient between the reinforcing portion and the base material is small, and the thermal shock resistance does not decrease. The term “kojierai powder” used in the present invention means “kojierai powder”

It refers to powder (2 M G_〇 · 2 A 1 ₂ 〇 ₃ · 5 S i 〇 _2), the chemical composition S i 〇 _2: 4 8-5 4 wt%, A 1 ₂ 〇 _3: 3 2 38% by mass, MgO: It is in the range of 12 to 18% by mass, and the main crystal phase is cordierite.

In addition, as described in Japanese Patent Application Laid-Open No. 2000-51710, a material obtained by attaching a “cordierite-forming raw material” to a substrate and then transforming the cordierite into a cordierite by a heat treatment is one that carries the “cordierite powder”. Therefore, the effects of the present invention cannot be obtained. Specifically, the thickness of the partition wall in the applied portion is increased, and the pressure loss is only increased, but the effect of improving the wear resistance is not recognized.

The “substrate” in the present invention means a honeycomb structure, that is, a cylindrical structure having a large number of cells (through holes) divided by a plurality of partition walls, and has an overall shape, size, number of cells, and the like. Although the shape and the like are not particularly limited, the present invention is particularly effective in a thin-walled 82 mm structure having a low abrasion resistance at the opening end face and a partition wall having a thickness of 100 m or less.

It is sufficient that the “reinforcing portion” is provided on at least one of the opening end surfaces of the base material, and it is not always necessary to have the “reinforcing portion” on both the opening end surfaces. This is because only one of the opening end surfaces is exposed toward the engine side and is exposed to high-pressure exhaust gas, so that it is only necessary to improve the wear resistance of that portion. However, it is preferable to have a reinforcing portion on both open end faces, regardless of the direction of arrangement.

The “reinforcing part” is denser and has a lower porosity than other parts, so it is preferable that the “reinforcing part” is formed in an excessively wide range in that the amount of supported catalyst decreases. I don't. Therefore, it is preferable that the reinforcing portion is provided only on the minimum portion capable of exhibiting the effect of improving the wear resistance, that is, on the entire opening end face of the honeycomb structure and the portion within 10 mm from the opening end face in the cell forming direction.

The term “supported” in the present invention means a state in which cordierite powder is fixed to a substrate in some form, and it is not necessary that cordierite after being supported is in a powdery state. For example, when the cordierite powder is supported on the substrate by heat treatment, a part of the cordierite powder becomes glassy and is fused to the substrate via the glass phase or completely melted depending on the temperature. Although it may be integrated with the material, the “support” in the present invention includes all such states.

Generally, the base material used is one manufactured by extrusion molding, but at the time when the slurry is applied, even if it is made of cogerite, it is made of a cogerite-forming material. If the base material is fired (hereinafter referred to as “fired body”), it is an unfired material (a material that has not been fired but has been dried only after extrusion molding. Dry body "). However, for those made of cordierite-forming raw materials and dried products, firing after loading is essential.

The method for supporting the cordierite powder is not particularly limited, and examples thereof include a spraying method, a brush coating method, and a method of impregnating and applying a slurry to a sponge or the like. It is preferable to use a method of immersing the base material and attaching the slurry, followed by drying and / or baking (a so-called diving method). This is because the dipping method can easily obtain a uniform carrying state.

When loading is carried out by the dipping method, in order to stabilize the slurry and enable uniform loading, the slurry is prepared using a cordierite powder having an average particle diameter of 1 Om or less as measured by the laser method. For example, water can be used as a dispersion medium of the slurry, but the concentration of the slurry is not particularly limited. However, the slurry is homogeneous and has little sediment. Preferably, the solid content concentration is about 10 to 60% by mass in order to prepare a tree.

If desired, additives such as surfactants used for ordinary slurry preparation may be added to the slurry.

Further, it is preferable to add an additive such as colloidal ceramic or glaze for strengthening the fixation between the collierite powder and the base material.

The term “colloidal ceramic” as used in the present invention means colloidal ceramic particles having an average particle diameter of 0.2 Aim or less. In this method, the base material is preferably a fired body because it enables uniform loading of the dielite powder and at the same time, heat treatment such as drying or baking evaporates the water of the colloidal material and develops a strong adhesive effect. If so, the effect of improving the abrasion resistance can be obtained simply by drying at a relatively low temperature of about 100 to 200 ° C. without firing after applying the slurry.

However, when the temperature is raised to about 140 ° C. near the melting point of cordierite (145 ° C.), a part of the cordierite powder becomes vitreous and becomes glassy. This is preferred because it is fused to the base material through the metal and firmly adhered, so that abrasion resistance is further improved. '' The type of colloidal ceramic is not particularly limited, but it is preferable to use colloidal silica or colloidal alumina, which can be easily obtained as a commercial product. The solid content ratio between the cordierite powder and the colloidal ceramic is about 5:95 to 20:80 in order to avoid the influence of large shrinkage when the colloidal ceramic is crystallized or glassed during the heat treatment. The mass ratio is preferably

As used herein, "glaze" refers to a formulation that forms a silicate compound glass after firing.

When this is added to the slurry together with the cordierite powder, it is possible to uniformly support the cordierite powder as in the case of the colloidal ceramic. Become. Also, since it has the effect of lowering the melting point of cordierite, it is relatively easy to fuse the cordierite powder to the base material or to fuse the cordierite powder and integrate it with the base material. Yes, and a strong fixation state can be obtained more easily.

It should be noted that the glaze, unlike the colloidal ceramic, exhibits a strong adhesive effect only after firing and vitrification. That is, in the case of glaze, the above effect cannot be obtained only by drying without firing.

The components constituting the glaze are not particularly limited, but it is preferable to use a feldspar-based glaze having a vitrification temperature of at least 250 ° C so as not to significantly lower the melting point of the glaze-attached portion of the base material. It is more preferable to use a cordierite glaze in which cordierite is preliminarily blended in an amount of about 30 to 40% by mass in order to reduce the coefficient of thermal expansion.

The above-mentioned cordierite glaze can be prepared by, for example, wet-charging a cordierite powder to be supported on a base material with a trommel together with glaze raw materials such as feldspar, silica, clay and the like, and mixing.

In this case, the cordierite powder in the glaze is of the same material as the cordierite powder to be supported on the base material, but differs in that it is a very fine powder, and forms part of the vitrified component. Will do.

As for the ratio between the cordierite powder and the glaze, as the glass component generated by the glaze increases, the glass tends to become brittle and the abrasion resistance decreases. Therefore, in the case of the kojierite glaze, it is preferable that the ratio between the kojierite powder and the glaze is approximately 1: 1.

The substrate to which the slurry is adhered as described above can form a reinforcing portion by drying and / or firing.

The term “drying” as used herein refers to an operation of removing the dispersion medium in the slurry at a relatively low temperature of about 100 to 200 ° C. and fixing the colloidal powder or the like in the slurry to the base material. Means On the other hand, “sintering” means that heat treatment at a relatively high temperature of about 500 to 140 ° C. It refers to the operation of sintering, fusing, melting and integrating light powder, etc., onto a substrate. Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(1) Preparation of sample

In Examples and Comparative Examples, a cylindrical shape having a diameter of 100 mm and a length of 100 mm, a partition wall thickness of 90 zm, and having square cells at a ratio of 62 cells / cm ² , an aperture ratio of 86 A fired body made of cordierite or a dried body made of a cordierite-forming material was used as a base material.

First, a slurry using water having the composition shown in Table 1 as a dispersion medium was prepared. For some of these, 1% by mass of nonionic surfactant was added to the total slurry mass.

Only a portion of the substrate up to 5 mm from the opening end face side in the cell forming direction was immersed in the slurry and pulled up. Next, the water and the like in the slurry were removed by blowing and drying at 150, and some of them were baked at 140 ° C to carry the cordierite powder on the substrate. Then, a honeycomb structure having a reinforcing portion was obtained (Examples 1 to 7, Comparative Examples 1 to 7).

(2) Evaluation method

With respect to the honeycomb structure samples of Examples and Comparative Examples, the wear resistance, the coefficient of thermal expansion, the porosity, and the average pore diameter were measured, and the performance was evaluated. The abrasion resistance was evaluated based on the volume of the abraded portion of the sample after performing the following tests.

First, a metal case containing a sample was connected to the exhaust port of a gasoline engine with a displacement of 2.2 liters and a displacement of 2.2 liters. That is, the sample was placed immediately adjacent to the engine. At this time, five iron balls with a diameter of 1.7 mm were inserted into the space between the reinforcement of the sample and the engine. According to such a method, in addition to being able to evaluate the wear resistance of the oxide scale generated in the actual use environment, the effect of improving the wear resistance can be evaluated in a short time.

The diameter of the iron ball was determined from the viewpoint that the iron ball did not pass through the square cell of the base material.

Next, after the engine was operated at 680 rpm for 5 minutes, the operation of performing the warm-up operation for 5 minutes was defined as one cycle, and the operation was continuously performed for 300 cycles. Then, the sample was taken out of the metal case, and the volume of the worn part of the sample worn by the iron ball was measured. The volume was measured simply by filling beads with 1.5 mm diameter in the abraded area and simply counting the number of beads.

Regarding the coefficient of thermal expansion (hereinafter referred to as “CTE”), the coefficient of linear thermal expansion in the direction perpendicular to the cell formation direction of the sample was measured, and it was 1.0 X 10: ⁶ Z ° C or less. things ◎, 1 2 X 1 0 - .. 6 Z ° C or less is intended to 〇, 1 2 X 1 0 _ ⁶ / super at which samples were evaluated as X.

The measurement was performed using a differential thermal dilatometer by calculating the difference in thermal expansion between the sample and the standard material at 40 to 800 ° C.

The porosity and the average pore diameter were evaluated by cutting out a part of the reinforcing portion from the 82-cam structure samples of the examples and comparative examples, and measuring the cut-out portion by a mercury intrusion method. (3) Result

As is evident from Table 1, the volume of the abraded portion was less than 40% by volume of the untreated product in each of the samples of Examples 1 to 7 in which the coredite powder was supported. Improvement was observed. Was also good with all ^{1. 2 X 1 0- 6 /} ° C or less for CTE.

In particular, in the sample of Example 7 in which colloidal silica was added and calcined, the abrasion resistance was remarkably improved, with the volume of the abraded portion being 10% by volume or less of the untreated product, and the CTE almost increased. It showed very good results in that it did not.

On the other hand, in the samples of Comparative Examples 1 to 5 supporting only the melting point lowering component of corgelite, although the value of porosity was reduced and densification was observed, even though the volume of the abraded portion was low, 50% of the untreated product was obtained. %, And the improvement in wear resistance was still insufficient. In addition, the sample of Comparative Example 5 was melted because the melting point depression was too large.

Furthermore, the samples other than Comparative Example 2 had a low effect of improving the wear resistance, and the value of CTE was significantly increased, which was presumed to be inferior in thermal shock resistance. Industrial applicability

As described above, the honeycomb structure of the present invention has a reinforcing portion holding at least one of the open end faces supporting the cordierite powder, so that the honeycomb structure has a thin wall type honeycomb structure having low pressure loss and the like. The advantage is not diminished, and the abrasion resistance of the opening end surface is excellent.

Claims

The scope of the claims

1. A cordierite honeycomb structure comprising a cordierite honeycomb substrate having at least one opening end face of a honeycomb structure base material having a reinforcement portion carrying cordierite powder.

2. The cordierite honeycomb structure according to claim 1, which has a reinforcing portion in which the cordierite powder is supported via a glass phase.

3. The cordierite 82-cam structure according to claim 1 or 2, having a reinforcing portion only at an opening end face of the base material and at a portion within 10 mm or less from the opening end face in a cell forming direction.

4. The cordierite honeycomb structure according to any one of claims 1 to 3, wherein the partition walls of the base material have a thickness of 100 or less.

5. After attaching a slurry containing a cordierite powder to at least one opening end surface of a baked or unfired honeycomb structure substrate made of a cordierite or a cordierite-forming raw material, drying and Z or firing. A method for producing a cordierite honeycomb structure.

6. The method for producing a cordierite 82 cam structure according to claim 5, wherein the slurry containing the cordierite powder and the colloidal ceramic is applied, followed by drying, burning, or firing.

7. The method for producing a cordierite honeycomb structure according to claim 5, wherein the slurry containing the cordierite powder and the glaze is adhered, then dried and fired.